Objective having long back focal distance with regard to its focal length

ABSTRACT

A photographic objective having a relatively long back focal distance with regard to its focal length and also having a great relative opening comprising in combination in front of the diaphragm a negative lens group comprising at least one component lens and spaced therefrom a preferably cemented positive lens element which comprises at least two component lenses having opposite refractive power. Behind the diaphragm a negative lens group is disposed which comprises at least one component lens.

O United States Patent 1111 [72] Inventors Walter Mandler; [56]References Cited Garry Edwards; Erich Wagner, 0 I I ml App No gg'g'sggCanada 1734, 424 1 2/1956 Bertele .1 4 1 350 215 [22] Filed July 13 19693,132,199 5/1964 Z1mmermann et a1 350/215 X 451 Patented July 6, 1971FOREIGN PATENTS [73] Assignee E rnst Leitz GmbH 878,879 10/1961 GreatBritain 350/215 Wetzlar, Germany 924,914 5/1963 Great Britain 350/215[32] Priority June 15, 1968 1,111,533 5/1968 Great Britain 350/225 5 7Primary Examiner--David Schonberg Assistant ExaminerPaul A. SacherAttorney-Krafft and Wells [54] OBJECTIVE HAVING LONG BACK FOCAL ABSTRACTA h p otographlc ob ectlve having a relatlvely DISTANCE REGARD TO ITSFOCAL long back focal distance with regard to its focal length andLENGTH also having a great relative opening comprising in combina- 6Clams 33 Drawmg Figs tion in front of the diaphragm a negative lensgroup compris- [52] US. Cl 350/215, ing at least one component lens andspaced therefrom a 350/209, 350/225 preferably cemented positive lenselement which comprises at [51] Int. Cl G02b 9/62 least two componentlenses having opposite refractive power. [50] Field of Search 350/209,Behind the diaphragm a negative lens group is disposed which 215, 225comprises at least one component lens.

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sum 8 BF 8 I QMM WALTERWANDLER OBJECTIVE HAVING LONG BACK FOCAL DISTANCEWITH REGARDTO ITS FOCAL LENGTH CROSS-REFERENCE TO RELATED APPLICATIONBACKGROUND OF THE INVENTION Our present invention relates tophotographic objectives, more specifically to wide-angle objectiveshaving a long back focal distance and a great relative opening.

It is well known in the art that the use of wide-angle objectives incombination with single lens reflex camera is rendered considerablydifficult, owing to the space required in the cameras for the tilting ofthe reflex mirror, as a consequence whereof the objectives have to havea rather long back focal distance. For this reason, it has al ady beensuggested to design such wide-angle objectives in the manner of invertedtelephoto lenses, so-called retrofocus lenses. However, this type ofobjective presents considerable difficulties in color correction withregard to the lateral aberrations. Besides, with this type only rathersmall relative openings can be attained if oversized dimensions are tobe avoided.

Further, there has been suggested to design the objectives in questionin symmetry to the diaphragm disposing on either side of the diaphragmpositive lens groups and, noticeably spaced therefrom, negative lensgroups, preferably negative menisci. Such objectives offer indeed goodpossibilities for correction, however, only objectives of short backfocal distances can be obtained this way, and they render the objectivesunsuitable for use with single lens reflex cameras. Unfortunately, anyincrease of the back focal distance leads to a reduction of the relativeopening.

It is, therefore, an object of the present invention to provideobjectives which overcome the above-mentioned disadvantages, arid it isa further object to provideobjectives which are inexpensive inmanufacture, even if the objectives comprise relatively many componentlenses.

SUMMARY OF THE INVENTION The above stated objects are attained withobjectives comprising in combination in front of the diaphragm anegative lens group consisting of at least one component lens and spacedtherefrom a positive lens element, "preferably cemen'ted from at leasttwo component lenses having opposite refractory power, and furthercomprising a negative lens group consisting of at least one componentlens behind the diaphragm. Preferably, the negative" lens group mountedin frontof the diaphragm includes exclusively refracting surfaces ofwhich the centers of curvature'are positioned :in the direction towards*the diaphragm. The'surface adjacent the diaphragm of the negative lensgroup directly behind this diaphragm and the surface adjacentthe imageplane'alsohave their-centers of curvature positioned in the directiontowards the diaphragm. Their. radiiare to be shorter than the totalfocal length. The object-side negative lens-group may comprise aplurality of menisci'with their concave surfaces being directed towardsthe diaphragm. The total focal length of these menisci is to be greaterthan thetotal focal length of the assembled objective. The focal lengthof the positive lens group in front of the diaphragm is to be smallerthan'thefocal length f-the entire objective.

DESCRIPTION'OF THE'DRAWINGS In Examples l to 6 are mentioned the exactdata of six objectives designed according to the invention. In theappending drawings:

FIGS. I-5 are axial sectional views of the objectives designed accordingto the data in Examples 1-6,

FIGS. 2a-e to 5a-d are graphs showing the state of correction of thecorresponding objectives, and

FIGS. 6af are a comparison drawing of these six objectives wherein alsothe focal lengths of the three individual lens groups are provided whicheach objective comprises, and wherein, further, the focal lengths of thelens groups are given which are positioned in front of the diaphragm.

Objectives of the above described type have a back focal length whichamounts to at least two-thirds of the total focal length of eachparticular objective.

From the field angles mentioned in the tables provided in the Examples,the efficiency of the new designing principle will be readily apparent.Even if only a total of four com- .ponent lenses is used'a relativeopening of f:4 can be achieved together with a picture angle of $157.

The following specific examples give the data of six objectives designedaccording to the invention:

EXAMPLE 1 The data-0f the radii r lens spacings a,,, lens thicknessesd,., focal lengths f and back focal distance s are as follows:

[Focal length=; Field angle==l=19.5; Relative opening=fz41 1 Space infront and behind said diaphragm.

EXAMPLE 2 The data of the radii r lens spacings a,,, lens thicknesses clfocal lengths 1),, back focal distance si and glass types having arefractive index w and Abbe I number 11 are as follows:

[Focal length=l00; Field anglc==l=31; Relative opcning=fz4l Spacein-front and behind said diaphragm.

EXAMPLE 3 The data of the radii r lens spacings a :lens thicknesses dfocal lengths f back focal distance s and glass types having arefractive index n. and Abbi a number 11 are as follows:

[Focal length- 100; Field angle -;l;37; Relative npening;f:2.8]

4. and glass types having a refractive index n and Abb We??? 2 a a f lswea.

[Focal length=100; Field angle==l=4fi; Relative opeiiing=i:3.4]

n- +il8.7ii =+9g 3 111:5.43 1. 62286 60. 0s d =5. 0 1. 59263 10.66 r7-=:+0i.2 f1=l26.5 rz=+61. 2a f -117. 0

' ai=th8fi l0 (1 18.3 D -"+101 .6 r +133. 3

71 :543 1. 62286 60. 08 (11 5. 0 1, 59263 40. 66 i=+60.75 r =+63. 27fi.2= 4

, 12:51.20 T=+60.10 fi ,2=+7l|.3 r +52. 00

43:30.72 1. 79227 47. 15 ai=2s. 3 1. 747115 +1. 4!! fi=+71.i I5 =-1s9.sl-09.8

ai=17.s1 1.81265 25. 24 d =16.2 1.7(l8i7 20.74 T7=549.3 T7=:1:

31 2.14 1 a3=2. 86 i GMT-3.35 aa2=(l.74 -56.39 Ts=46.08

- 4 :11.20 1.62286 0110s d =1l).4 1. 50205 46.88 Yo=71.58 T s 61. 23

ai=2.34 20 m=2. 17 in=+ Tw=l365.0

(10:13.61 1. 72823 37. 85 d5: 12. 5 1. 68585 47. 92 r i=-36.08 /;:-375.0F4633 -790.0

d1=0.00 1.81265 25. 24 1 6 1 7 347 2 74 l1=" ri2=81.37

0 :13.61 =12. 5 n;=-34.62 25 Tiu=- 8 11,:4143 1. 62408 as. 11 0 56181 9sii=6 .00 r =--4il.66

. lm filiBlff 'l" #52925 9Pm1?DQEF LLEQB MQEEB; Ma-

EXAMPLE 4 EXAMPLE 6 data of the radii Tm lens spacings. The photographicobjective has the following specifications: thicknesses d focal lengthsf,,, back focal distgnge bs ti i d n an e ais e misses n a e .8 100.thefieldangle is :50",

[Focal length=100; Field angle==l=40; Relative openliig=f:2.8] therelative Opening iS f:3.4,

and wherein IL: v the comprised negative front lens element consists ofthree 40 single menisci which are concave in the direction towards then=+94.30 diaphragm, r2=+63l17 a,=5.44 1. 62286 60.08 IFAMA said meniscihaving I,

r a =19.83 a focal length fi l22.8, said negative front lens elementIFEM "6228 M08 being spaced from the subsequent positive cemented lensn=+M.63 16 element by a distance u,=43.9, said positive lens element,5=+5g 67 f +g5 6 having a focal length f =+70.0, the space in front and99 37 47-15 +74 0 behind said diaphragm is u =9.45, the comprisednegative 81265 25,24 2 lens element behind said diaphragm consists ofthree menisci r =1422.18 a 121 50 which are concave in the directiontowards said diaphragm 3: 1 m and of which two menisci are cemented andone is a single 7 =-51.2o

8 15:11.28 1' 62286 m 08 meniscus, the focal length of said lens elementbeing rq=62.40 2 ,-;=405.5, the back focal distance is s =68.9, thefocal a =2.3 H U W HFHESO' ii 136 172823 s7 s5 lengihlsf 5 7 -9.

6 i I {8:43.123 What we claim is. I

d =6.0 1.81265 25. 24 l. A wide-angle photographic ob ective fortransmitting the TIP-9M5 =13 image of an object through a diaphragm toan image plane, -35'.52 I said objective having a relatively long backfocal distance with m: 4,125 regard to its focal cal length and a greatrelative opening, said s=(l4.M objective consisting of in combination:first negative lens means positioned between said object and 1 Space infront and behind said diaphragm. said diaphragm; Y r M cemented positivelens means having at least two lenses having opposite refractive power,said positive lens means l' ,m... .4 .t. EXAMPLL positioned between saidfirst negative lens means and said The data of the radii 7 lens spacingsa,,, lens p g thicknesses (i focal lengths f,,, back focal distance 8second negative lens means positioned between said diaphragm and saidimage plane, wherein the focal length is 100, the field angle is :50,the relative opening isf:3.4, and wherein g we said first negative lensmeans consists of three single menisci which are concave in thedirection towards the diaphragm, said menisci having a focal length fl22.8. said first negative lens means being spaced from said positivelens means by a distance (1, 43.9, said positive lens means having afocal length fl=+70.0, the space in front and behind said diaphragm is a=9.45, said second negative lens means consists of three menisci whichare concave in the direction towards said diaphragm and of which twomenisci are cemented and one is a single meniscus, the focal length ofsaid lens means beingfi=405.5, the back focal distance is s 68.9, thefocal length isf 2 I A n 2. A wide-angle photographic objectivefortransmitting the image of an object through a diaphragm to an imageplane, said objective having a relatively long back focal distance withregard to its focal length and a great relative opening, said objectiveconsisting of in combination:

first negative lens means positioned between said object and saiddiaphragm; cemented positive lens means having at least two lenseshaving opposite refractive power, said positive lens means positionedbetweensaid first negative lens means and said diaphragm; and secondnegative lens means positioned between said diaphragm and said imageplane v he -ein the data of the radii r... lens spacings a", lensthicknesses d", focal lengtllSfn and back focal distance s are asfollows:

[Focal length 19.5"; Relative opening =f: 4]

I Space in front and behind said diaphragm.

the data of the radii r lens spacings a lens thicknesses d focal lengthsf.,, hack focal distance 8 and glass types having a refractive index 11and Abbe number 1), are as follows:

1 Space in front and behind said diaphragm.

4. A wide-angle photographic objective for transmitting the image of anobject through a diaphragm to an image plane, said objective having arelatively long back focal distance with regard to its focal length anda great relative opening, said objective consisting of in combination:

first negative lens means positioned between said object and saiddiaphragm;

cemented positive lens means having at least two lenses having oppositerefractive power, said positive lens means positioned between said firstnegative lens means and said diaphragm; and

second negative lens means positioned between said diaphragm and saidimage plane, wherein the data of the radii r lens spacings a,,, lensthicknesses d focal lengths f back focal distance s and glass typeshaving a refractive index n and Abbe number 0 are as follows:

[Foca1length=100; Field ang1e=:l;37; Relative opening=f:2.8]

n=:+98.7ti

d1 5.43 1. 62286 60. 08 Tz=+61.20 f =126.5

dz=5A3 1. 62286 60. 08 n=+60.75 r,.1=+79.a

az=5l.20 r +60,10

(IF-30.72 1. 79227 47. 16 hi -91.2n f2=+71 (ii -17.61 1. 81206 25. 24T:=- -54!l.3

(In 214 1 so (132 835 l ds 11.2l) 1. 62286 60. 08 r :-71.58

(10 13.61 1. 72823 37. 85 55 ne -36.02; f;=376.0

aa 13.6l I f13 -34.62

(1 5.43 1. 62408 36. 11 fu=-6l. 00 81 65.70

Space in front and behind said diaphragm.

5. A wide-angle photographic ob ective for transmitting the image of anobject through a diaphragm to an image plane, said objective having arelatively long back focal distance with regard to its focal length anda great relative opening, said objective consisting of in combination:

b first negative lens means positioned between said object and the dataof the radii T lens spacing a lens thicknesses d,,, focal lengths f backfocal distance s and glass types having a refractive index 11 and Abbenumber 11 are as follows:

[Focal lvngth lOO; Field anglc iwio"; Relative opcning fzilfll 1 Spacein front and behind said diaphragm 6. A wide-angle photographicobjective for transmitting the image of an object through a diaphragm toan image plane, said objective having a relatively long back focaldistance with regard to its focal length and a great relative opening,said objective consisting of in combination;

first negative lens means positioned between said object and saiddiaphragm cemented positive lens means having at least two lenses havingopposite refractive power, said positive lens means positioned betweensaid first negative lens means and said diaphragm; and second negativelens means positioned between said diaphragm and said image plane,wherein the data of the radii r lens spacings an, lens thicknesses d,,,focal lengths f back focal distance s and glass types having arefractive index n and Abbe number w are as follows:

[Focal length: 1110; Field anglr ifl; Relative ()llUlllilP, f:3. l]

(l1 5. (l 1. 50203 40. 66 T2 +61. 23 f1 --117.l)

(ll n 18. 3 i +133. 3

(I 5. (l 1. 592(l3 40. 66 1 +6327 f1,z +88. 1

(1;; 28. 3 1. 74796 44. 49 Tu 18l|. 3 fa -H5914 1L: 16. 2 1.76847 26. 74T7 :l:=

Llai Z. 1 aa2=6. 74 1 rt:-46. 08

d :10. 4 1. 56295 46. 88 rs) li1. .23

(#2. 17 Tm 13(i5. 0

(In -12. 5 1. 68585 47. U2 Tu -'.l(l. H3 f3 ---7ll0.

d p- 6.0 1. 56181 60. J6 m -l.). (35

1 Space in [rent and behind said diaphragm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 257Dated y 5, 1

Inventor(s) Walter Mandler; Garry Edwards; Erich Wagner It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 5, line 9 focal length "-22. 8" should read -122. 8

Signed and sealed this lltth day of December 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTISCHALK Attesting Officer ActingCommissioner of Patents FORM PO-105Q (10-59] sc 5 7e-p5 n u.s GOVERNMENTPRINTING OFFICE 1N9 0-356-334

1. A wide-angle photographic objective for transmitting the image of anobject through a diaphragm to an image plane, said objective having arelatively long back focal distance with regard to its focal cal lengthand a great relative opening, said objective consisting of incombination: first negative lens means positioned between said objectand said diaphragm; cemented positive lens means having at least twolenses having opposite refractive power, said positive lens meanspositioned between said first negative lens means and said diaphragm;second negative lens means positioned between said diaphragm and saidimage plane, wherein the focal length is 100, the field angle is + OR -50*, the relative opening is f:3.4, and wherein said First negative lensmeans consists of three single menisci which are concave in thedirection towards the diaphragm, said menisci having a focal length f1-122.8, said first negative lens means being spaced from said positivelens means by a distance a1 43.9, said positive lens means having afocal length f2 +70.0, the space in front and behind said diaphragm isa2 9.45, said second negative lens means consists of three menisci whichare concave in the direction towards said diaphragm and of which twomenisci are cemented and one is a single meniscus, the focal length ofsaid lens means being f3 -405.5, the back focal distance is s'' 68.9,the focal length is f1,2 +77.9.
 2. A wide-angle photographic objectivefor transmitting the image of an object through a diaphragm to an imageplane, said objective having a relatively long back focal distance withregard to its focal length and a great relative opening, said objectiveconsisting of in combination: first negative lens means positionedbetween said object and said diaphragm; cemented positive lens meanshaving at least two lenses having opposite refractive power, saidpositive lens means positioned between said first negative lens meansand said diaphragm; and second negative lens means positioned betweensaid diaphragm and said image plane, wherein
 3. A wide-anglephotographic objective for transmitting the image of an object through adiaphragm to an image plane, said objective having a relatively longback focal distance with regard to its focal length and a great relativeopening, said objective consisting of in combination; first negativelens means positioned between said object and said diaphragm; cementedpositive lens means having at least two lenses having oppositerefractive power, said positive lens means positioned between said firstnegative lens means and said diaphragm; and second negative lens meanspositioned between said diaphragm and said image plane, wherein
 4. Awide-angle photographic objective for transmitting the image of anobject through a diaphragm to an image plane, said objective having arelatively long back focal distance with regard to its focal length anda great relative opening, said objective consisting of in combination:first negative lens means positioned between said object and saiddiaphragm; cemented positive lens means having at least two lenseshaving opposite refractive power, said positive lens means positionedbetween said first negative lens means and said diaphragm; and secondnegative lens means positioned between said diaphragm and said imageplane, wherein
 5. A wide-angle photographic objective for transmittingthe image of an object through a diaphragm to an image plane, saidobjective having a relatively long back focal distance with regard toits focal length and a great relative opening, said objective consistingof in combination: first negative lens means positioned between saidobject and said diaphragm; cemented positive lens means having at leasttwo lenses having opposite refractive power, said positive lens meanspositioned between said first negative lens means and said diaphragm;and second negative lens means positioned between said diaphragm andsaid image plane, wherein
 6. A wide-angle photographic objective fortransmitting the image of an object through a diaphragm to an imageplane, said objective having a relatively long back focal distance withregard to its focal length and a great relative opening, said objectiveconsisting of in combination; first negative lens means positionedbetween said object and said diaphragm; cemented positive lens meanshaving at least two lenses having opposite refracTive power, saidpositive lens means positioned between said first negative lens meansand said diaphragm; and second negative lens means positioned betweensaid diaphragm and said image plane, wherein